[clf]

Originally Posted by Phil

Thank you CLF,
I appreciate the advice.
I know the ISO should be as low as possible, but I also thought, from my own experience that the shutter speed should be kept to no more than around 20 seconds? If I go over that I end up with trails from the stars.

That is a good point about the star trails, it was a field I never had enough patience in, but I would imagine that you would have more than 20 seconds to work with. Is your tripod heavy enough for the camera/lens set up? Use mirror lock up if you have it. (I am imagining your star trails are quite short, but a noticeable blur and even minor movement in your tripod legs could explain that)

In the first image, the light source was the moon. It was a full moon and was creating so much light you could easily see where you were walking, even though we were in the middle of nowhere with absolutely no artificial light.

In a full moon, I wouldnt waste time trying to capture stars, however, if you hold a dark card near to the lens to create a shadow over it, it will help immensely.

Can you explain your comment about what is demonstrated by the silhouette of the trees?

look into the silhouette of the trees, and you can see yellow, red and green dots (I couldnt understand the yellow, I assumed it to be post edit, but the moon creating highlights on the leaves will explain that). The red and green dots are I believe 'noise' borne from the sensor sensitivity set too high (ie 3200). I reckon if you magnify to around 400%, you may see some but fewer blue dots showing up. The sensor if a Bayer arrangement (which most DSLR use), is more sensitive to red and particularly green (due to the 'arrangement' of the RGB filter assembly above the sensor, and differing wavelengths of RG and B), and turning up the ISO on a DSLR increases the sensitivity of the sensor electrically. This effectively boosts the 'power' of the pixels, so when you get green and red like that, they are effectively operating at their max capacity. ie Getting too much light and burning out. Having the sensor exposed for long periods can also introduce electrical interference and with a high ISO can make it unstable and unpredictable which adds another noise issue - I hope that makes sense, the image below shows pictorially the difference between a Foveon (Sigma cameras use these) and a Bayer Array sensor. There are other types of sensor, and quite a few more seem to have come along since I stopped following camera development.

I hope the above makes sense, it is a very crude explanation but there will be more involved explanations online about it.